US9537512B2ActiveUtilityPatentIndex 72
Method and a system implementing a turbo-diversity scheme for wireless OFDM systems
Est. expiryJul 18, 2032(~6 yrs left)· nominal 20-yr term from priority
Inventors:LORCA HERNANDO JAVIER
H04L 1/0066H03M 13/2771H04L 5/0007H03M 13/2792H04L 1/065H04L 5/001H04L 1/0606H04L 1/0631H04L 1/0668H04B 7/02H03M 13/258H04L 1/0071H04B 7/024H04B 7/0413H04L 1/06H04L 1/00
72
PatentIndex Score
5
Cited by
17
References
7
Claims
Abstract
The method comprising passing, a base station or a user terminal, information comprising data signals and encoding, a first and a second turbo encoders, said received data signals, generating two different turbo code blocks comprising a set of systematic and parity bits. Where, in order to enhance detection the two different turbo code blocks are simultaneously transmitted through a wireless OFDM system and wherein the data signals to be encoded by said second turbo encoder are interleaved prior encoding by an external bit interleaver. The system of the invention is arranged to implement the method of the invention.
Claims
exact text as granted — not AI-modifiedThe invention claimed is:
1. A method for implementing a turbo-diversity scheme in a wireless orthogonal frequency division multiplex (OFDM) system, the method comprising:
encoding, at a first turbo encoder and a second turbo encoder, information comprising data signals, and generating two different turbo code blocks each comprising a set of systematic and parity bits;
interleaving, by an external bit interleaver, the data signals to be encoded by said second turbo encoder;
de-interleaving said systematic bits after the second turbo encoder, and applying an Alamouti-based space-frequency block coding (SFBC) over said de-interleaved systematic bits after the second turbo encoder and said systematic bits after the first turbo encoder; and
simultaneously transmitting each of said two different turbo code blocks over different transmit antennas through said wireless OFDM system.
2. The method according to claim 1 , wherein said two different turbo code blocks generated are further processed using processing techniques according to any of a rate matching technique, scrambling, interleaving, or modulation mapping.
3. The method according to claim 1 , further comprising separating from said two different turbo code blocks symbols carrying the systematic bits from symbols carrying the parity bits at a receiver side, and further performing Alamouti-based SFBC decoding to the symbols carrying the systematic bits and a Zero-forcing, minimum mean squared error (MMSE), maximum likelihood (ML), or other multiple input multiple output (MIMO) decoding technique to the symbols carrying the parity bits.
4. The method according to claim 3 , further comprising obtaining Log-Likelihood Ratio values (LLR) corresponding to said symbols carrying systematic bits and said symbols carrying parity bits using the expression:
LLR
(
b
l
)
=
ln
∑
t
∈
S
l
+
f
(
t
^
|
t
)
∑
t
∈
S
l
-
f
(
t
^
|
t
)
where S l + ,S l − denote a set of constellation symbols whose l-th bit is 1 and 0, respectively, and f is a conditional probability density function (PDF) of {circumflex over (t)} given that symbol t was transmitted.
5. The method according to claim 4 , further comprising decoding upon reception said symbols carrying systematic and parity bits by exploiting the outputs from each turbo decoding iteration of one transmit antenna as extrinsic information to the other transmit antenna, with appropriate interleaving or de-interleaving of the extrinsic information depending on the transmit antenna under consideration, using the expressions:
y (1) [k]=y s [k]+L 12 (1) [k]+c (1) L 21 (1) [k]+c (2→1) L e (2→1)
y (2) [k ]=Intl{ y s [k]}+L 12 (2) [k]+c (2) L 21 (2) [k]+c (1→2) L e (1→2)
where y (1) [k], y (2) [k] are the LLR values after a given iteration of the first turbo decoder and the second turbo decoder respectively; L 12 (1) , L 21 (1) and L 12 (2) , L 21 (2) represent mutual information terms exchanged by internal constituent decoders of the first turbo decoder and the second turbo decoder respectively; c (1) , c (2) are extrinsic scaling factors for the first turbo decoder and the second Unix) decoder respectively; c (2→1) , c (1→2) are mutual scaling factors for extrinsic information exchange between the second turbo decoder and the first turbo decoder, and between the first turbo decoder and the second turbo decoder, respectively; L e (2→1) =Intl −1 {y (2) [k]} is de-interleaved output from a previous iteration of the second turbo decoder and L e (1→2) =Intl{y (1) [k]} is interleaved output from a previous iteration of the first turbo decoder.
6. The method according to claim 5 , further comprising decoding upon reception, using a successive interference cancellation technique, said symbols carrying parity bits through reconstruction and cancellation of interference at each received block caused by the other transmit antenna, using the expressions:
r
1
(
1
)
′
=
r
1
-
h
12
t
^
2
=
h
11
t
1
+
n
1
(
1
)
′
r
2
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1
)
′
=
r
2
-
h
22
t
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2
=
h
21
t
1
+
n
2
(
1
)
′
⋮
r
M
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1
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r
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2
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h
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1
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1
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r
1
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2
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1
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r
2
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2
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where r j denote signals received by antenna RX j; r j (1) , r j (2) denote signals corresponding to both coded blocks that come from the antenna RX j after removal of interference; n j (1) ′,n j (2) ′ are complex baseband noise terms; h ij are complex channel transfer elements between TX antenna j and RX antenna i; and {circumflex over (t)} 1 , {circumflex over (t)} 2 denote estimated symbols transmitted by TX antennas 1 and 2 respectively.
7. A system for turbo-diversity in a wireless orthogonal frequency division multiplex (OFDM) system, the system comprising:
a base station and at least a user terminal transmitting and receiving data signals through said wireless OFDM system;
a first turbo encoder and a second turbo encoder configured to encode said data signals received and to generate two different turbo code blocks each comprising a set of systematic and parity bits;
an external interleaver unit arranged to said second turbo encoder and configured to interleave the data signals prior to being encoded by the second turbo encoder;
a de-interleaver configured de-interleave the systematic bits after the second turbo encoder;
an Alamouti-based space-frequency block coding (SFBC) applied over said de-interleaved systematic bits after the second turbo encoder and said systematic bits after the first turbo encoder; and
a transmitter configured to transmit each of said two different turbo code blocks over different transmit antennas.Cited by (0)
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